Reset crossing and clock crossing interface for integrated circuit generation

ABSTRACT

Systems and methods are disclosed for generation and testing of integrated circuit designs with clock crossings between clock domains and reset crossings between reset domains. These may allow for the rapid design and testing (e.g. silicon testing) of processors and SoCs. Clock crossings may be automatically generated between modules, inferring the values of design parameters, such as a signaling protocol (e.g. a bus protocol), directionality, and/or a clock crossing type (e.g., synchronous, rational divider, or asynchronous), of a clock crossing. Reset crossings may be automatically generated in a similar manner. For example, implicit classes may be used to generate clock crossings or reset crossings in a flexible manner. For example, these system and methods may be used to rapidly connect a custom processor design, including one or more IP cores, to a standard input/output shell for a SoC design to facilitate rapid silicon testing of the custom processor design.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.17/157,564, which was filed on Jan. 25, 2021, which is a continuation inpart of U.S. patent application Ser. No. 16/506,507, which was filed onJul. 9, 2019. The content of the foregoing applications are incorporatedherein by reference in its entirety for all purposes.

TECHNICAL FIELD

This disclosure relates to a reset crossing and clock crossing interfaceto facilitate generation of integrated circuit designs.

BACKGROUND

Integrated circuits are typically designed and tested in a multi-stepprocess that involves multiple specialized engineers performing avariety of different design and verification tasks on an integratedcircuit design. A variety of internal or proprietary (e.g.company-specific) integrated circuit design tool chains are typicallyused by these engineers to handle different parts of the integratedcircuit design workflow of using commercial electronic design automation(EDA) tools. Some integrated circuits use multiple clocks and includemultiple clock domains. A clock domain crossing is circuitry used toreliably transfer digital signals from one clock domain to another. Forexample, clock domain crossings are described in Verma, S., et al.,“Understanding Clock Domain Crossing Issues,” EE Times, Dec. 24, 2007.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is best understood from the following detaileddescription when read in conjunction with the accompanying drawings. Itis emphasized that, according to common practice, the various featuresof the drawings are not to-scale. On the contrary, the dimensions of thevarious features are arbitrarily expanded or reduced for clarity.

FIG. 1 is block diagram of an example of an integrated circuit designincluding an input/output shell.

FIG. 2 is block diagram of an example of an integrated circuit designincluding the input/output shell and custom processor logic.

FIG. 3 is block diagram of an example of a system for facilitatingdesign and manufacture of integrated circuits.

FIG. 4 is block diagram of an example of a system for facilitatingdesign of integrated circuits.

FIG. 5 is flow chart of an example of a process for generating a clockcrossing of a clock crossing type in an integrated circuit design.

FIG. 6 is flow chart of an example of a process for generating a clockcrossing in an integrated circuit design.

FIG. 7 is flow chart of an example of a process for facilitating designof integrated circuits.

FIG. 8 is flow chart of an example of a process for fabricating andtesting of an integrated circuit based on a modified register-transferlevel data structure.

FIG. 9 is block diagram of an example of an integrated circuit designincluding the input/output shell and custom processor logic.

FIG. 10 is flow chart of an example of a process for generating a resetcrossing of a reset crossing type in an integrated circuit design.

FIG. 11 is flow chart of an example of a process for generating a resetcrossing in an integrated circuit design.

FIG. 12 is flow chart of an example of a process for generating a resetcrossing to accommodate a difference in reset durations between modulesin different reset domains in an integrated circuit design.

DETAILED DESCRIPTION

Systems and methods for providing a clock crossing interface tofacilitate generation of integrated circuit designs are describedherein. A user is able to issue a command that causes automaticgeneration of a clock crossing between two modules in aregister-transfer level representation of an integrated circuit designthat are in different clock domains. Passing digital signals betweendifferent clock domains can cause problems in an integrated circuit,such as metastability, data loss, and/or data incoherency. A clockcrossing includes logic (e.g., a multi-flop synchronizer, MUXrecirculation, handshake, or a first in first out (FIFO) buffer) at thedestination module and/or at the source module to address one or more ofthese problems.

The specifics of a clock crossing to be generated may be determinedbased on data of one or both of the modules being connected by the clockcrossing. A system may automatically determine a signaling protocol(e.g., a bus protocol) for the clock crossing based on data for one orboth of the modules being connected by the clock crossing. A system mayautomatically determine a directionality (e.g., sending or receiving)for the clock crossing based on data for one or both of the modulesbeing connected by the clock crossing. In some implementations, a systemmay automatically determine a clock crossing type (e.g., synchronous,rational, or asynchronous) for the clock crossing based on data for oneor both of the modules being connected by the clock crossing (e.g.,based on the clock frequencies of the two modules). In someimplementations, the clock crossing type is selected based on aparameter of the command.

For example, a non-bus module may be connected to a bus module by addinga clock crossing. For example, two bus modules may be connected using aclock crossing. In some implementations, a first module may be connectedto two other modules in different clock domains using clock crossing ofdifferent clock crossing types to the first module. For example, amodule of a custom processor design may be connected to a module of aninput/output shell for an integrated circuit that is a system-on-a-chip,which may enable rapid silicon testing of the custom processor design.

Similarly, systems and methods for providing a reset crossing interfaceto facilitate generation of integrated circuit designs are describedherein. A user is able to issue a command that causes automaticgeneration of a reset crossing between two modules in aregister-transfer level representation of an integrated circuit designthat are in different reset domains. Passing digital signals betweendifferent reset domains can cause problems in an integrated circuit,such as metastability, data loss, and/or data incoherency. A resetcrossing includes logic (e.g., latches and/or counters for stretching areset signal and/or suppressing outputs of a module during its resetperiod) at the destination module and/or at the source module to addressone or more of the problems.

The specifics of a reset crossing to be generated may be determinedbased on data of one or both of the modules being connected by the resetcrossing. A system may automatically determine a signaling protocol(e.g., a bus protocol) for the reset crossing based on data for one orboth of the modules being connected by the reset crossing. A system mayautomatically determine a directionality (e.g., sending or receiving)for the reset crossing based on data for one or both of the modulesbeing connected by the reset crossing. In some implementations, a systemmay automatically determine a reset crossing type (e.g., synchronouswith a duration difference, synchronous-to-asynchronous, orasynchronous) for the reset crossing based on data for one or both ofthe modules being connected by the reset crossing (e.g., based on thereset domain types and/or reset durations of the two modules). In someimplementations, the reset crossing type is selected based on aparameter of the command.

In a first aspect, the subject matter described in this specificationcan be embodied in methods that include accessing a register-transferlevel data structure for an integrated circuit design; receiving acommand to generate a clock crossing between a first module of theregister-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determining a signaling protocol identifier for the clockcrossing based on data of the second module; responsive to the command,automatically determining a directionality for the clock crossing basedon data of the second module; and responsive to the command,automatically generating the clock crossing between the first module andthe second module based on the signaling protocol identifier and basedon the directionality to obtain a modified register-transfer level datastructure.

In a second aspect, the subject matter described in this specificationcan be embodied in systems that include a network interface, a memory,and a processor, wherein the memory includes instructions executable bythe processor to cause the system to: access a register-transfer leveldata structure for an integrated circuit design; receive a command togenerate a clock crossing between a first module of theregister-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determine a signaling protocol identifier for the clockcrossing based on data of the second module; responsive to the command,automatically determine a directionality for the clock crossing based ondata of the second module; and responsive to the command, automaticallygenerate the clock crossing between the first module and the secondmodule based on the signaling protocol identifier and based on thedirectionality to obtain a modified register-transfer level datastructure.

In a third aspect, the subject matter described in this specificationcan be embodied in a non-transitory computer-readable storage mediumthat includes instructions that, when executed by a processor,facilitate performance of operations comprising: accessing aregister-transfer level data structure for an integrated circuit design;receiving a command to generate a clock crossing between a first moduleof the register-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determining a signaling protocol identifier for the clockcrossing based on data of the second module; responsive to the command,automatically determining a directionality for the clock crossing basedon data of the second module; and responsive to the command,automatically generating the clock crossing between the first module andthe second module based on the signaling protocol identifier and basedon the directionality to obtain a modified register-transfer level datastructure.

In a fourth aspect, the subject matter described in this specificationcan be embodied in methods that include accessing a register-transferlevel data structure for an integrated circuit design; receiving acommand to generate a reset crossing between a first module of theregister-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determining a signaling protocol identifier for the resetcrossing based on data of the second module; responsive to the command,automatically determining a directionality for the reset crossing basedon data of the second module; and responsive to the command,automatically generating the reset crossing between the first module andthe second module based on the signaling protocol identifier and basedon the directionality to obtain a modified register-transfer level datastructure.

In a fifth aspect, the subject matter described in this specificationcan be embodied in systems that include a network interface, a memory,and a processor, wherein the memory includes instructions executable bythe processor to cause the system to: access a register-transfer leveldata structure for an integrated circuit design; receive a command togenerate a reset crossing between a first module of theregister-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determine a signaling protocol identifier for the resetcrossing based on data of the second module; and responsive to thecommand, automatically generate the reset crossing between the firstmodule and the second module based on the signaling protocol identifierto obtain a modified register-transfer level data structure.

In a sixth aspect, the subject matter described in this specificationcan be embodied in a non-transitory computer-readable storage mediumthat includes instructions that, when executed by a processor,facilitate performance of operations comprising: accessing aregister-transfer level data structure for an integrated circuit design;receiving a command to generate a reset crossing between a first moduleof the register-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determining a signaling protocol identifier for the resetcrossing based on data of the second module; responsive to the command,automatically determining a directionality for the reset crossing basedon data of the second module; and responsive to the command,automatically generating the reset crossing between the first module andthe second module based on the signaling protocol identifier and basedon the directionality to obtain a modified register-transfer level datastructure.

Some implementations may provide advantages over prior systems andmethods, such as automating significant parts of integrated circuitdesign flow; helping to enable fast silicon testing of new processordesigns when used with a system-on-a-chip input/output design; andreducing development and testing time for integrated circuits.

FIG. 1 is block diagram of an example of an integrated circuit design100 including an input/output shell. The integrated circuit 110 includesa clock generation module 120 and a collection of interface modules(130, 140, 150, and 160) connected to pins of the integrated circuit.The interface modules include a TileLink PBus module 130; a ChipLinkmodule 140; a JTAG module 150; and a USB module 160, which each are intheir own respective clock domains. For example, the modules of thisinput/output shell may provide a standard interface transferring data tobetween one or more processors, which may be added to the integratedcircuit design 100, and external devices (e.g., a silicon testingapparatus). The input/output shell of the integrated circuit design 100can thus be used to facilitate rapid testing of a new processor designin silicon.

For example, the clock generation module 120 may include ahigh-frequency crystal, a phase locked loop, an oscillator, a switch,and/or a real-time clock. For example, the TileLink PBus module mayinclude pins for mode selection, a Serial Peripheral Interface (SPI), anInter-Integrated Circuit (I2C), a Universal AsynchronousReceiver/Transmitter (UART), a pulse width modulation (PWM), and/orGeneral Purpose Input/Output (GPIO).

FIG. 2 is block diagram of an example of an integrated circuit design200 including the input/output shell of FIG. 1 and custom processorlogic. The integrated circuit 210 includes custom modules (220, 222,230, 232, 234, and 236) in three clock domains: core_clk, tl_clk, andlim_clk; along with interface modules of the input/output shell (130,140, 150, and 160) in their four respective clock domains; p_clk,cl_clk, jtag_clk, and usb_clk. A user may quickly merge the customprocessor logic with the input/output shell by issuing commands to causeclock crossings to be automatically generated between modules indifferent clock domains of the integrated circuit 210. In this example,the custom processor logic of the integrated circuit design 200 includesa first IP core module 220 and a second IP core module 222 that areconnected to a TileLink SBus module 230 by a rational clock crossing(RCC) 240 and a rational clock crossing 242. A debug module 232 in thetl_clk clock domain is connected to the JTAG module 150 in the jtag_clkclock domain by an asynchronous clock crossing (ACC) 252. A mask ROMmodule 234 is also included in the tl_clk clock domain and may beconnected to the TileLink SBus module 230 by intra-clock domainconnections (not explicitly shown in FIG. 2). A LIM SRAM module 236 inthe lim_clk clock domain is connected to the TileLink SBus module 230 bya rational clock crossing 244. The ChipLink module 140 in the cl_clkclock domain is connected to the TileLink SBus module 230 by a rationalclock crossing 246. The TileLink PBus module 130 in the p_clk clockdomain is connected to the TileLink SBus module 230 by an asynchronousclock crossing 250. The USB module 160 in the usb_clk clock domain isconnected to the TileLink SBus module 230 by an asynchronous clockcrossing 254. For example, the process 500 of FIG. 5 or the process 600of FIG. 6 may be implemented to generate the clock crossings (240, 242,244, 246, 250, 252, and 254) between the modules of the integratedcircuit design 200. The resulting integrated circuit design 200 may thenbe rapidly tested using system 300 of FIG. 3, the process 700 of FIG. 7and/or the process 800 of FIG. 8.

FIG. 3 is block diagram of an example of a system 300 for facilitatingdesign and manufacture of integrated circuits. The system 300 includes,the network 306, the integrated circuit design service infrastructure310, an FPGA/emulator server 320, and a manufacturer server 330. Forexample, a user may utilize a web client or a scripting API client tocommand the integrated circuit design service infrastructure 310 toautomatically generate an integrated circuit design based a set ofdesign parameter values selected by the user for one or more templateintegrated circuit designs. In some implementations, a user may issue acommand to the integrated circuit design service infrastructure 310 togenerate a clock crossing between modules of a register-transfer leveldata structure for an integrated circuit.

For example, the integrated circuit design service infrastructure 310may invoke (e.g., via network communications over the network 306)testing of the resulting design that is performed by the FPGA/emulationserver 320 that is running one or more FPGAs or other types of hardwareor software emulators. For example, the integrated circuit designservice infrastructure 310 may invoke a test using a field programmablegate array, programmed based on a field programmable gate arrayemulation data structure, to obtain an emulation result. The fieldprogrammable gate array may be operating on the FPGA/emulation server320, which may be a cloud server. Test results may be returned by theFPGA/emulation server 320 to the integrated circuit design serviceinfrastructure 310 and relayed in a useful format to the user (e.g., viaa web client or a scripting API client).

The integrated circuit design service infrastructure 310 may alsofacilitate the manufacture of integrated circuits using the integratedcircuit design in a manufacturing facility associated with themanufacturer server 330. In some implementations, a physical designspecification (e.g., a GDSII file) based on a physical design datastructure for the integrated circuit is transmitted to the manufacturerserver 330 to invoke manufacturing of the integrated circuit (e.g.,using manufacturing equipment of the associated manufacturer). Forexample, the manufacturer server 330 may host a foundry tape out websitethat is configured to receive physical design specifications (e.g., as aGDSII file or an OASIS file) to schedule or otherwise facilitatefabrication of integrated circuits. In some implementations, theintegrated circuit design service infrastructure 310 supportsmulti-tenancy to allow multiple integrated circuit designs (e.g., fromone or more users) to share fixed costs of manufacturing (e.g.,reticle/mask generation, and/or shuttles wafer tests). For example, theintegrated circuit design service infrastructure 310 may use a fixedpackage (e.g., a quasi-standardized packaging) that is defined to reducefixed costs and facilitate sharing of reticle/mask, wafer test, andother fixed manufacturing costs. For example, the physical designspecification may include one or more physical designs from one or morerespective physical design data structures in order to facilitatemulti-tenancy manufacturing.

In response to the transmission of the physical design specification,the manufacturer associated with the manufacturer server 330 mayfabricate and/or test integrated circuits based on the integratedcircuit design. For example, the associated manufacturer (e.g., afoundry) may perform optical proximity correction (OPC) and similarpost-tapeout/pre-production processing, fabricate the integratedcircuit(s) 332, update the integrated circuit design serviceinfrastructure 310 (e.g., via communications with a controller or a webapplication server) periodically or asynchronously on the status of themanufacturing process, performs appropriate testing (e.g., wafertesting) and send to packaging house for packaging. A packaging housemay receive the finished wafers or dice from the manufacturer and testmaterials, and update the integrated circuit design serviceinfrastructure 310 on the status of the packaging and delivery processperiodically or asynchronously. In some implementations, status updatesmay be relayed to the user when the user checks in using the webinterface and/or the controller might email the user that updates areavailable.

In some implementations, the resulting integrated circuits 332 (e.g.,physical chips) are delivered (e.g., via mail) to a silicon testingservice provider associated with a silicon testing server 340. In someimplementations, the resulting integrated circuits 332 (e.g., physicalchips) are installed in a system controlled by silicon testing server340 (e.g., a cloud server) making them quickly accessible to be run andtested remotely using network communications to control the operation ofthe integrated circuits 332. For example, a login to the silicon testingserver 340 controlling a manufactured integrated circuit 332 may be sentto the integrated circuit design service infrastructure 310 and relayedto a user (e.g., via a web client). For example, the integrated circuitdesign service infrastructure 310 may implement the process 700 of FIG.7 to control testing of one or more integrated circuits 332, which maybe structured based on a register-transfer level data structure (e.g., amodified register-transfer level data structure determined using theprocess 500 of FIG. 5 or the process 600 of FIG. 6). For example, theintegrated circuit design service infrastructure 310 may implement theprocess 800 of FIG. 8 to control fabrication and silicon testing of oneor more integrated circuits 332, which may be structured based on aregister-transfer level data structure (e.g., a modifiedregister-transfer level data structure determined using the process 500of FIG. 5 or the process 600 of FIG. 6).

FIG. 4 is block diagram of an example of a system 400 for facilitatingdesign of integrated circuits. The system 400 is an example of aninternal configuration of a computing device that may be used toimplement the integrated circuit design service infrastructure 310 as awhole or one or more components of the integrated circuit design serviceinfrastructure 310 of the system 300 shown in FIG. 3. The system 400 caninclude components or units, such as a processor 402, a bus 404, amemory 406, peripherals 414, a power source 416, a network communicationinterface 418, a user interface 420, other suitable components, or acombination thereof.

The processor 402 can be a central processing unit (CPU), such as amicroprocessor, and can include single or multiple processors havingsingle or multiple processing cores. Alternatively, the processor 402can include another type of device, or multiple devices, now existing orhereafter developed, capable of manipulating or processing information.For example, the processor 402 can include multiple processorsinterconnected in any manner, including hardwired or networked,including wirelessly networked. In some implementations, the operationsof the processor 402 can be distributed across multiple physical devicesor units that can be coupled directly or across a local area or othersuitable type of network. In some implementations, the processor 402 caninclude a cache, or cache memory, for local storage of operating data orinstructions.

The memory 406 can include volatile memory, non-volatile memory, or acombination thereof. For example, the memory 406 can include volatilememory, such as one or more DRAM modules such as DDR SDRAM, andnon-volatile memory, such as a disk drive, a solid state drive, flashmemory, Phase-Change Memory (PCM), or any form of non-volatile memorycapable of persistent electronic information storage, such as in theabsence of an active power supply. The memory 406 can include anothertype of device, or multiple devices, now existing or hereafterdeveloped, capable of storing data or instructions for processing by theprocessor 402. The processor 402 can access or manipulate data in thememory 406 via the bus 404. Although shown as a single block in FIG. 4,the memory 406 can be implemented as multiple units. For example, asystem 400 can include volatile memory, such as RAM, and persistentmemory, such as a hard drive or other storage.

The memory 406 can include executable instructions 408, data, such asapplication data 410, an operating system 412, or a combination thereof,for immediate access by the processor 402. The executable instructions408 can include, for example, one or more application programs, whichcan be loaded or copied, in whole or in part, from non-volatile memoryto volatile memory to be executed by the processor 402. The executableinstructions 408 can be organized into programmable modules oralgorithms, functional programs, codes, code segments, or combinationsthereof to perform various functions described herein. For example, theexecutable instructions 408 can include instructions executable by theprocessor 402 to cause the system 400 to automatically, in response to acommand, generate an integrated circuit design and associated testresults based on a design parameters data structure. The applicationdata 410 can include, for example, user files, database catalogs ordictionaries, configuration information or functional programs, such asa web browser, a web server, a database server, or a combinationthereof. The operating system 412 can be, for example, MicrosoftWindows®, Mac OS X®, or Linux®; an operating system for a small device,such as a smartphone or tablet device; or an operating system for alarge device, such as a mainframe computer. The memory 406 can compriseone or more devices and can utilize one or more types of storage, suchas solid state or magnetic storage.

The peripherals 414 can be coupled to the processor 402 via the bus 404.The peripherals 414 can be sensors or detectors, or devices containingany number of sensors or detectors, which can monitor the system 400itself or the environment around the system 400. For example, a system400 can contain a geospatial location identification unit, such as aglobal positioning system (GPS) location unit. As another example, asystem 400 can contain a temperature sensor for measuring temperaturesof components of the system 400, such as the processor 402. Othersensors or detectors can be used with the system 400, as can becontemplated. In some implementations, the power source 416 can be abattery, and the system 400 can operate independently of an externalpower distribution system. Any of the components of the system 400, suchas the peripherals 414 or the power source 416, can communicate with theprocessor 402 via the bus 404.

The network communication interface 418 can also be coupled to theprocessor 402 via the bus 404. In some implementations, the networkcommunication interface 418 can comprise one or more transceivers. Thenetwork communication interface 418 can, for example, provide aconnection or link to a network, such as the network 306, via a networkinterface, which can be a wired network interface, such as Ethernet, ora wireless network interface. For example, the system 400 cancommunicate with other devices via the network communication interface418 and the network interface using one or more network protocols, suchas Ethernet, TCP, IP, power line communication (PLC), WiFi, infrared,GPRS, GSM, CDMA, or other suitable protocols.

A user interface 420 can include a display; a positional input device,such as a mouse, touchpad, touchscreen, or the like; a keyboard; orother suitable human or machine interface devices. The user interface420 can be coupled to the processor 402 via the bus 404. Other interfacedevices that permit a user to program or otherwise use the system 400can be provided in addition to or as an alternative to a display. Insome implementations, the user interface 420 can include a display,which can be a liquid crystal display (LCD), a cathode-ray tube (CRT), alight emitting diode (LED) display (e.g., an OLED display), or othersuitable display. In some implementations, a client or server can omitthe peripherals 414. The operations of the processor 402 can bedistributed across multiple clients or servers, which can be coupleddirectly or across a local area or other suitable type of network. Thememory 406 can be distributed across multiple clients or servers, suchas network-based memory or memory in multiple clients or serversperforming the operations of clients or servers. Although depicted hereas a single bus, the bus 404 can be composed of multiple buses, whichcan be connected to one another through various bridges, controllers, oradapters.

FIG. 5 is flow chart of an example of a process 500 for generating aclock crossing of a clock crossing type in an integrated circuit design.The process 500 includes accessing 510 a register-transfer level datastructure for an integrated circuit design; receiving 520 a command togenerate a clock crossing between a first module of theregister-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determining 530 a signaling protocol identifier for theclock crossing based on data of the second module; responsive to thecommand, automatically determining 540 a directionality for the clockcrossing based on data of the second module; responsive to the command,automatically generating 560 the clock crossing between the first moduleand the second module based on the signaling protocol identifier andbased on the directionality to obtain a modified register-transfer leveldata structure; and transmitting, storing, or displaying 570 themodified register-transfer level data structure. For example, theprocess 500 may be implemented by the system 300 of FIG. 3. For example,the process 500 may be implemented by the system 400 of FIG. 4.

The process 500 includes accessing 510 a register-transfer level datastructure (e.g., a file, a database, a repository, or a bitstream) foran integrated circuit design. The register-transfer level data structureincludes a logical description of an integrated circuit design. Forexample, the integrated circuit design may be of an IP core. Forexample, the integrated circuit design may be of a processor. Forexample, the integrated circuit design may be of a system-on-a-chip. Insome implementations, the register-transfer level data structure maydescribe a system-on-a-chip including a custom processor and aninput/output shell configured to transfer to and/or from devicesexternal to the system-on-a-chip. For example, the register-transferlevel data structure may describe the integrated circuit of 210 of FIG.2. For example, the register-transfer level data structure may beaccessed 510 by receiving the register-transfer level data structure(e.g., via network communications using the network communicationsinterface 418). For example, the register-transfer level data structuremay be accessed 510 by reading the register-transfer level datastructure from memory (e.g., reading from the memory 406 via the bus404).

The process 500 includes receiving 520 a command to generate a clockcrossing between a first module of the register-transfer level datastructure and a second module of the register-transfer level datastructure. The command may include a parameter specifying a clockcrossing type (e.g., synchronous, rational, or asynchronous). Forexample, the command may identify the first module and the second moduleas two modules of the integrated circuit design to be connected with aclock crossing. For example, the command may include a call to a methodof the first module or a method of the second module. In someimplementations, the command may have been generated using a graphicaluser interface that displays graphical representations of the modules ofthe register-transfer level data structure. For example, the command maybe part of an application programming interface (API). For example, thecommand may be received 520 via a user interface (e.g., the userinterface 420). For example, the command may be received 520 via anetwork interface (e.g., using the network communications interface418). In some implementations, the command is generated as a result of auser interface interaction by a human user. In some implementations, thecommand is generated by an automatically by an EDA design flow.

The process 500 includes, responsive to the command, automaticallydetermining 530 a signaling protocol identifier for the clock crossingbased on data of the second module. The signaling protocol identifiermay identify a signaling protocol (e.g., a bus protocol) to be used onthe clock crossing. For example, the signaling protocol used by a clockcrossing may be the AMBA AXI4 protocol, the TileLink protocol, or aninterrupt protocol. For example, the signaling protocol identifier mayinclude text, an integer, or some other data that may be mapped toparticular signaling protocol. In some implementations, the signalingprotocol identifier for the clock crossing is determined 530 based on abus protocol of the second module (e.g., where the second module is abus). In some implementations, the signaling protocol identifier for theclock crossing is determined 530 based on data of the first module. Forexample, the signaling protocol identifier for the clock crossing may bedetermined 530 as corresponding to a signaling protocol that is commonto the first module and the second module. For example, determining 530the signaling protocol identifier for the clock crossing may includeaccessing a signaling protocol identifier of the first module and/or asignaling protocol identifier of the second module.

The process 500 includes, responsive to the command, automaticallydetermining 540 a directionality (e.g., sending vs. receiving or mastervs. slave) for the clock crossing based on data of the second module.For example, the directionality of the clock crossing may be determined540 as receiving at the first module and sending from the second module.For example, the directionality of the clock crossing may be determined540 as sending from the first module and receiving at the second module.For example, where the second module is a bus, the directionality of theclock crossing may be determined 540 based on whether the first moduleis configured to be a master or a slave on the bus.

The process 500 includes, responsive to the command, automaticallygenerating 560 the clock crossing between the first module and thesecond module based on the signaling protocol identifier and based onthe directionality to obtain a modified register-transfer level datastructure. For example, the clock crossing may be automaticallygenerated 560 based on the clock crossing type (e.g., synchronous,rational, or asynchronous) specified by the command. In someimplementations, generating 560 the clock crossing includes using animplicit class (e.g., an implicit class defined in the SCALA language)that is invoked using the signaling protocol identifier. In someimplementations, generating 560 the clock crossing includes using anauto-punching wires method to connect the first module to the secondmodule. For example, the clock crossing may include a logic circuitadded to the first module and a logic circuit added to the second moduleto facilitate passing of signals on one or more conductors across aclock domain boundary. For example, a clock crossing may be generated560 to include multiple re-synchronization flip-flops in the receivingmodule (e.g., the first module or the second module). For example, aclock crossing may be generated 560 to include logic for a MUXrecirculation synchronizer in the receiving module (e.g., the firstmodule or the second module). For example, a clock crossing with anasynchronous clock crossing type may be generated 560 to include logicfor a FIFO in the receiving module (e.g., the first module or the secondmodule). For example, a clock crossing with an asynchronous clockcrossing type may be generated 560 to include logic for handshake in thereceiving module and the sending module (e.g., the first module or thesecond module). The modified register-transfer level data structure(e.g., a file, a database, a repository, or a bitstream) includes thegenerated 560 clock crossing.

For example, the second module may be a bus module. For example, thefirst module may be a processor module and it may be connected by theclock crossing to a bus module (e.g., a TileLink bus) that is in adifferent clock domain of the integrated circuit (e.g., asystem-on-a-chip). In some implementations, the first module is part ofa custom processor design and second module is part of input/outputshell (e.g., the input/output shell of FIG. 1). For example, the firstmodule may include an IP core and the second module may be a componentof an input/output shell for a system-on-a-chip design. In someimplementations, the first module and the second module are both busmodules. For example, the clock crossing may be generated 560 to includelogic in the first module and/or the second module to convert signalsfrom a first bus protocol to a second compatible bus protocol and viceversa.

The process 500 includes transmitting, storing, or displaying 570 themodified register-transfer level data structure (e.g., a file, adatabase, a repository, or a bitstream). For example, theregister-transfer level data structure may be transmitted 570 to anexternal device (e.g., a personal computing device) for display orstorage. For example, the register-transfer level data structure may bestored 570 in memory (e.g., the memory 406). For example,register-transfer level data structure may be displayed 570 in a userinterface (e.g., the user interface 420). For example, theregister-transfer level data structure may be transmitted 570 via anetwork communications interface (e.g., the network communicationsinterface 418).

Although the process 500 is shown as a series of operations for clarity,implementations of the process 500 or any other technique, process, oralgorithm described in connection with the implementations disclosedherein can be performed in various orders or concurrently. Additionally,operations in accordance with this disclosure can be performed withother operations not presented and described herein. For example, theprocess 500 of FIG. 5 may repeated to receive 520 additional commands toadd additional clock crossings to the modified register-transfer leveldata structure. Furthermore, one or more aspects of the systems andtechniques described herein can be omitted. For example, operation 530or the operation 540 may be omitted from the process 500 where thesignaling protocol identifier and/or the directionality for the clockcrossing are provided as parameters of the command received 520.

The process 500 may enable the generation of multiple clock crossingsto/from a module that are of different clock crossing types. Forexample, the process 500 may be repeated such that the command is afirst command and the clock crossing is a first clock crossing, and therepeated process may include receiving 510 a second command to generatea second clock crossing between the first module of theregister-transfer level data structure and a third module of theregister-transfer level data structure; responsive to the secondcommand, automatically determining 530 a signaling protocol identifierfor the second clock crossing based on data of the third module;responsive to the second command, automatically determining 540 adirectionality for the second clock crossing based on data of the thirdmodule; and responsive to the second command, automatically generating560 the second clock crossing between the first module and the thirdmodule based on the signaling protocol identifier for the second clockcrossing and based on the directionality for the second clock crossingto obtain the modified register-transfer level data structure. Thesecond clock crossing may have a different clock crossing type (e.g.,synchronous and rational, or rational and asynchronous) than the firstclock crossing. For example a module may be connected to two differentbuses in different clock domains using different types of clockcrossings.

FIG. 6 is flow chart of an example of a process 600 for generating aclock crossing in an integrated circuit design. In this example, theclock crossing type (e.g., synchronous, rational, or asynchronous) ofthe clock crossing is automatically determined based on data of one ormore of the modules being connected by the clock crossing. The process600 includes accessing 610 a register-transfer level data structure foran integrated circuit design; receiving 620 a command to generate aclock crossing between a first module of the register-transfer leveldata structure and a second module of the register-transfer level datastructure; responsive to the command, automatically determining 630 asignaling protocol identifier for the clock crossing based on data ofthe second module; responsive to the command, automatically determining640 a directionality for the clock crossing based on data of the secondmodule; responsive to the command, automatically determining 650 a clockcrossing type for the clock crossing based on a clock frequency of thefirst module and based on a clock frequency of the second module;responsive to the command, automatically generating 660 the clockcrossing between the first module and the second module based on thesignaling protocol identifier, based on the directionality, and based onthe clock crossing type to obtain a modified register-transfer leveldata structure; and transmitting, storing, or displaying 670 themodified register-transfer level data structure. For example, theprocess 600 may be implemented by the system 300 of FIG. 3. For example,the process 600 may be implemented by the system 400 of FIG. 4.

The process 600 includes accessing 610 a register-transfer level datastructure (e.g., a file, a database, a repository, or a bitstream) foran integrated circuit design. The register-transfer level data structureincludes a logical description of an integrated circuit design. Forexample, the integrated circuit design may be of an IP core. Forexample, the integrated circuit design may be of a processor. Forexample, the integrated circuit design may be of a system-on-a-chip. Insome implementations, the register-transfer level data structure maydescribe a system-on-a-chip including a custom processor and aninput/output shell configured to transfer to and/or from devicesexternal to the system-on-a-chip. For example, the register-transferlevel data structure may describe the integrated circuit 210 of FIG. 2.For example, the register-transfer level data structure may be accessed610 by receiving the register-transfer level data structure (e.g., vianetwork communications the network communications interface 418). Forexample, the register-transfer level data structure may be accessed 610by reading the register-transfer level data structure from memory (e.g.,reading from the memory 406 via the bus 404).

The process 600 includes receiving 620 a command to generate a clockcrossing between a first module of the register-transfer level datastructure and a second module of the register-transfer level datastructure. For example, the command may identify the first module andthe second module as two modules of the integrated circuit design to beconnected with a clock crossing. For example, the command may include acall to a method of the first module or a method of the second module.In some implementations, the command may have been generated using agraphical user interface that displays graphical representations of themodules of the register-transfer level data structure. For example, thecommand may be part of an application programming interface (API). Forexample, the command may be received 620 via a user interface (e.g., theuser interface 420). For example, the command may be received 620 via anetwork interface (e.g., using the network communications interface418). In some implementations, the command is generated as a result of auser interface interaction by a human user. In some implementations, thecommand is generated by an automatically by an EDA design flow.

The process 600 includes, responsive to the command, automaticallydetermining 630 a signaling protocol identifier for the clock crossingbased on data of the second module. The signaling protocol identifiermay identify a signaling protocol (e.g., a bus protocol) to be used onthe clock crossing. For example, the signaling protocol used by a clockcrossing may be the AMBA AXI4 protocol, the TileLink protocol, or aninterrupt protocol. For example, the signaling protocol identifier mayinclude text, an integer, or some other data that may be mapped toparticular signaling protocol. In some implementations, the signalingprotocol identifier for the clock crossing is determined 630 based on abus protocol of the second module (e.g., where the second module is abus). In some implementations, the signaling protocol identifier for theclock crossing is determined 630 based on data of the first module. Forexample, the signaling protocol identifier for the clock crossing may bedetermined 630 as corresponding to a signaling protocol that is commonto (e.g., supported by) the first module and the second module. Forexample, determining 630 the signaling protocol identifier for the clockcrossing may include accessing a signaling protocol identifier of thefirst module and/or a signaling protocol identifier of the secondmodule.

The process 600 includes, responsive to the command, automaticallydetermining 640 a directionality (e.g., sending vs. receiving or mastervs. slave) for the clock crossing based on data of the second module.For example, the directionality of the clock crossing may be determined640 as receiving at the first module and sending from the second module.For example, the directionality of the clock crossing may be determined640 as sending from the first module and receiving at the second module.For example, where the second module is a bus module, the directionalityof the clock crossing may be determined 640 based on whether the firstmodule is configured to be a master or a slave on the bus.

The process 600 includes, responsive to the command, automaticallydetermining 650 a clock crossing type for the clock crossing based on aclock frequency of the first module and based on a clock frequency ofthe second module. In some implementations, the clock crossing type isdetermined as the simplest (e.g., smallest area or lowest power)applicable clock crossing type given the clock frequencies of the twomodules. For example, where the clock frequencies of the two modulesbeing connected are the same, the clock crossing type may be determined650 to be synchronous. For example, where the clock frequencies of thetwo modules being connected are different but related by a rationaldivisor, he clock crossing type may be determined 650 to be rational.For example, where the clock frequencies of the two modules beingconnected are not related by a rational divisor, the clock crossing typemay be determined 650 to be asynchronous.

The process 600 includes, responsive to the command, automaticallygenerating 660 the clock crossing between the first module and thesecond module based on the signaling protocol identifier and based onthe directionality to obtain a modified register-transfer level datastructure. For example, the clock crossing may be automaticallygenerated 660 based on the determined 650 clock crossing type (e.g.,synchronous, rational, or asynchronous). In some implementations,generating 660 the clock crossing includes using an implicit class(e.g., an implicit class defined in the SCALA language) that is invokedusing the signaling protocol identifier. In some implementations,generating 660 the clock crossing includes using an auto-punching wiresmethod to connect the first module to the second module. For example,the clock crossing may include a logic circuit added to the first moduleand a logic circuit added to the second module to facilitate passing ofsignals on one or more conductors across a clock domain boundary. Forexample, a clock crossing may be generated 660 to include multiplere-synchronization flip-flops in the receiving module (e.g., the firstmodule or the second module). For example, a clock crossing may begenerated 660 to include logic for a MUX recirculation synchronizer inthe receiving module (e.g., the first module or the second module). Forexample, a clock crossing with an asynchronous clock crossing type maybe generated 660 to include logic for a FIFO in the receiving module(e.g., the first module or the second module). For example, a clockcrossing with an asynchronous clock crossing type may be generated 660to include logic for handshake in the receiving module and the sendingmodule (e.g., the first module or the second module). The modifiedregister-transfer level data structure (e.g., a file, a database, arepository, or a bitstream) includes the generated 660 clock crossing.

For example, the second module may be a bus module. For example, thefirst module may be a processor module and it may be connected by theclock crossing to a bus module (e.g., a TileLink bus) that is in adifferent clock domain of the integrated circuit (e.g., asystem-on-a-chip). In some implementations, the first module is part ofa custom processor design and second module is part of input/outputshell (e.g., the input/output shell of FIG. 1). For example, the firstmodule may include an IP core and the second module may be a componentof an input/output shell for a system-on-a-chip design. In someimplementations, the first module and the second module are both busmodules. For example, the clock crossing may be generated 660 to includelogic in the first module and/or the second module to convert signalsfrom a first bus protocol to a second compatible bus protocol and viceversa.

The process 600 includes transmitting, storing, or displaying 670 themodified register-transfer level data structure (e.g., a file, adatabase, a repository, or a bitstream). For example, theregister-transfer level data structure may be transmitted 670 to anexternal device (e.g., a personal computing device) for display orstorage. For example, the register-transfer level data structure may bestored 670 in memory (e.g., the memory 406). For example,register-transfer level data structure may be displayed 670 in a userinterface (e.g., the user interface 420). For example, theregister-transfer level data structure may be transmitted 670 via anetwork communications interface (e.g., the network communicationsinterface 418).

Although the process 600 is shown as a series of operations for clarity,implementations of the process 600 or any other technique, process, oralgorithm described in connection with the implementations disclosedherein can be performed in various orders or concurrently. Additionally,operations in accordance with this disclosure can be performed withother operations not presented and described herein. For example, theprocess 600 of FIG. 6 may repeated to receive 620 additional commands toadd additional clock crossings to the modified register-transfer leveldata structure. Furthermore, one or more aspects of the systems andtechniques described herein can be omitted. For example, operation 630or the operation 640 may be omitted from the process 600 where thesignaling protocol identifier and/or the directionality for the clockcrossing are provided as parameters of the command received 620.

The process 600 may enable the generation of multiple clock crossingsto/from a module that are of different clock crossing types. Forexample, the process 600 may be repeated such that the command is afirst command and the clock crossing is a first clock crossing, and therepeated process may include receiving 620 a second command to generatea second clock crossing between the first module of theregister-transfer level data structure and a third module of theregister-transfer level data structure; responsive to the secondcommand, automatically determining 630 a signaling protocol identifierfor the second clock crossing based on data of the third module;responsive to the second command, automatically determining 640 adirectionality for the second clock crossing based on data of the thirdmodule; responsive to the second command, automatically determining 650a clock crossing type for the second clock crossing based on a clockfrequency of the first module and based on a clock frequency of thethird module; and responsive to the second command, automaticallygenerating 660 the second clock crossing between the first module andthe third module based on the signaling protocol identifier for thesecond clock crossing and based on the directionality for the secondclock crossing to obtain the modified register-transfer level datastructure. The second clock crossing may have a different clock crossingtype (e.g., synchronous and rational, or rational and asynchronous) thanthe first clock crossing. For example a module may be connected to twodifferent buses in different clock domains using different types ofclock crossings.

FIG. 7 is flow chart of an example of a process 700 for facilitatingdesign of integrated circuits. The process 700 includes accessing 710 adesign parameters data structure; generating 720 a register-transferlevel data structure for an integrated circuit based on the designparameters data structure; generating 722 one or more clock crossingsbetween modules of the register-transfer level data structure to obtaina modified register-transfer level data structure; generating 730 asoftware development kit for the integrated circuit based on themodified register-transfer level data structure; generating 740 aphysical design data structure for the integrated circuit based on themodified register-transfer level data structure; generating 750documentation for the integrated circuit based on the modifiedregister-transfer level data structure; generating 760 a fieldprogrammable gate array emulation data structure for the integratedcircuit based on the modified register-transfer level data structure andthe software development kit; generating 770 a test plan for anintegrated circuit based on the design parameters data structure andacceptance criteria; invoking 780 tests for the integrated circuit basedon the test plan, the modified register-transfer level data structure,the software development kit, and the physical design data structure toobtain a set of test results; and transmitting, storing, or displaying790 a design data structure based on the modified register-transferlevel data structure, the software development kit, the physical designdata structure, and the test results. The process 700 may automaticallygenerate and test an integrated circuit design conforming to designparameter values in a design parameters data structure in response to asingle command (e.g., a build command). For example, the process 700 maybe implemented by the integrated circuit design service infrastructure310 of FIG. 3. For example, the process 700 may be implemented by thesystem 400 of FIG. 4. For example, the process 700 may be used toquickly incorporate a modular processor design with an input/outputshell (e.g., the input/output shell of the integrated circuit design 100of FIG. 1), including connecting modules of the design usingautomatically generated clock crossings, in a system-on-a-chip designthat can be rapidly tested. This approach may reduce processordevelopment time, reduce the costs of testing a design, and/or improvethe quality of test results.

The process 700 includes accessing 710 a design parameters datastructure (e.g., a file, a database, a repository, or a bitstream). Thedesign parameters data structure includes values of design parameters ofan integrated circuit design. For example, the integrated circuit designmay be of an IP core. For example, the integrated circuit design may beof a system-on-a-chip. For example, the design parameters data structuremay include a JSON file. For example the design parameters of the designparameters data structure may include whether privilege modes aresupported, whether multiply extension is supported, whether floatingpoint extension is supported, whether error-correcting codes aresupported in on-chip memory, the size of an instruction cache, anassociativity of the instruction cache, a size of a data subsystem inon-chip memory, whether a port (e.g., a front port, a system port, aperipheral port, or a memory port) are included, a count of memory portchannels, a port communication protocol selection, a bus width, a countof physical memory protection units, whether JTAG debugging issupported, a count of hardware breakpoints, whether instruction tracingis supported, whether debug direct memory access is supported, a countof local interrupts, whether a platform level interrupt controller issupported, a count of interrupt priority levels, a count of globalinterrupts, whether branch prediction is supported, a count of branchtarget buffer entries, a count of branch history table entries, and/or aselection of a manufacturing process. For example, the design parametersdata structure may be accessed 710 by receiving the design parametersdata structure (e.g., via network communications with a web client or ascripting API client using the network communications interface 418).For example, the design parameters data structure may be accessed 710 byreading the design parameters data structure from memory (e.g., readingfrom the memory 406 via the bus 404).

The process 700 includes generating 720 a register-transfer level datastructure for an integrated circuit based on the design parameters datastructure. For example, design parameters data structure may include aJSON file listing identifiers of design parameters and correspondingvalues. In some implementations, the design parameters data structurealso includes an indication (e.g., a pointer, a name, or anotheridentifier) that identifies a template integrated circuit design thatthe design parameters modify. For example, the template integratedcircuit design may include modular design data structures that adhere toconventions for facilitating modular design. For example, generating 720the register-transfer level data structure for the integrated circuitbased on the design parameters data structure may include invoking aregister-transfer level service with data based on the design parametersdata structure.

For example, the register-transfer level data structure may include oneor more Verilog files. The register-transfer level data structure mayinclude updated configuration settings to drive later stages of anintegrated circuit design pipeline. In some implementations, theregister-transfer level data structure includes a memory map, one ormore port assignments, and floorplan information.

The register-transfer level data structure (e.g., a register-transferlevel file) may be automatically generated 720 based on the designparameters data structure using tools, such as Scala, Chisel, Diplomacy,and/or FIRRTL. For example, generating 720 the register-transfer leveldata structure for the integrated circuit may include executing Scalacode to read the design parameters data structure and dynamicallygenerate a circuit graph. In some implementations, generating 720 theregister-transfer level data structure for the integrated circuitincludes invoking a Diplomacy package in Chisel to determine a busprotocol for the integrated circuit.

The process 700 includes generating 722 one or more clock crossingsbetween modules of the register-transfer level data structure to obtaina modified register-transfer level data structure. For example, theprocess 500 of FIG. 5 may be implemented to generate 722 the one or moreclock crossings in the modified register-transfer level data structure.For example, the process 600 of FIG. 6 may be implemented to generate722 the one or more clock crossings in the modified register-transferlevel data structure.

The process 700 includes generating 730 a software development kit forthe integrated circuit based on the modified register-transfer leveldata structure. In some implementations, generating 730 the softwaredevelopment kit for the integrated circuit includes generating loadersfor a Verilog simulator and a physical field programmable gate array tobe flashed. For example, generating 730 the software development kit mayinclude accessing an existing toolchain or software development kit fora template integrated circuit design that is identified by the designparameters data structure. The existing toolchain or softwaredevelopment kit (e.g., a RISC-V toolchain/SDK) may be set up usingconventions suitable for configurability. For example, the existingtoolchain or software development kit may be organized into submodulescorresponding to design parameters of the design parameters datastructure. For example, the software development kit may include acompiler, an assembler, header files, libraries, boot loaders, kerneldrivers, and/or other tools for a fully functional SDK/computingenvironment. For example, generating 730 the software development kitmay include executing a Python script. In some implementations,generating 730 the software development kit includes parsing theregister-transfer level data structure (e.g., a JSON file), generatingoptions for the tools and builds, generating header files responsive toa memory map, selecting appropriate examples from the existing toolchainor software development kit, generating relevant configuration files fortarget simulators (e.g., QEMU (Quick Emulator)) so they can run the newdesign on another processor (e.g., x86), and generating loaders forVerilog simulators and physical FPGA boards to be flashed. The resultingsoftware development kit may be built and tested in the cloud (e.g.,before giving to customer). For example, generating 730 the softwaredevelopment kit may include invoking a software development kit servicewith data based on the modified register-transfer level data structureand/or the design parameters data structure.

The process 700 includes generating 740 a physical design data structure(e.g., a physical design file) for the integrated circuit based on themodified register-transfer level data structure. For example, generating740 a physical design data structure for the integrated circuit mayinclude invoking a physical design service with data based on themodified register-transfer level data structure and/or the designparameters data structure. For example, generating 740 a physical designdata structure for the integrated circuit may include invoking synthesisand place & route tools (e.g., Synopsys, Cadence, and/or Mentor tools).For example, generating 740 a physical design data structure for theintegrated circuit may include performing logical equivalent checking.For example, generating 740 a physical design data structure for theintegrated circuit may include invoking static timing analysis tools.For example, generating 740 a physical design data structure for theintegrated circuit may include performing design rule checking (DRC)and/or layout versus schematic (LVS) checking. For example, generating740 a physical design data structure for the integrated circuit mayinclude determining power, performance, and area estimates for theresulting integrated circuit design and providing these estimates asfeedback to a user (e.g., a user of a web client). For example, thephysical design data structure may include in less-technical termswhether there are any issues with the physical design. For example, thephysical design data structure may highlight important components of theoutput of the synthesis and place & route tools. For example, thephysical design data structure may include a GDSII file or an OASISfile. For example, generating 740 a physical design data structure forthe integrated circuit may include managing and orchestrating physicaldesign toolchains in a cloud. For example, generating 740 a physicaldesign data structure for the integrated circuit may include handlingdatabase movement from tool to tool, and managing access to third partyIP cores. For example, generating 740 a physical design data structurefor the integrated circuit may include accessing template designs, whichmay allow for significant design reuse. For example, generating 740 aphysical design data structure for the integrated circuit may includeidentifying those combinations to reduce workload. For example,generating 740 a physical design data structure for the integratedcircuit may provide better or more compact error/issue reporting, bytranslating tool issues into manageable feedback and providing theactual error/output of tools in a deliverable format to a user (e.g., auser of a web client). For example, generating 740 a physical designdata structure for the integrated circuit may include using physicaldesign blocks for identified pairings of functional blocks that may bereused across designs to improve efficiency.

The process 700 includes generating 750 documentation for the integratedcircuit based on the modified register-transfer level data structure.For example, generating 750 documentation for the integrated circuit mayinclude using Prince (available at https://www.princexml.com/). Forexample, generating 750 documentation for the integrated circuit mayinclude using ASCII Doc (available at http://asciidoc.org/). Forexample, generating 750 documentation for the integrated circuit mayinclude accessing a pre-loaded modular manual for a template integratedcircuit design that is identified by the design parameters datastructure. The modular manual may be set up using conventions suitablefor configurability. For example, the modular manual may be organizedinto submodules corresponding to design parameters of the designparameters data structure. In some implementations, the modular manualis stored as multiple components in corresponding directories of anexisting SDK for the template. Generating 750 documentation for theintegrated circuit may include generalizing the pre-loaded modularmanual to respond to values of design parameters in the designparameters data structure. For example, the generated 750 documentationmay be in an HTML format and/or in a PDF format. In order to correctlydocument the memory map/ports, generating 750 documentation for theintegrated circuit may include working with the post-RTL output. Forexample, generating 750 documentation for the integrated circuit mayinclude utilizing a documentation framework similar to the Reactframework (e.g., a JS HTML framework). In some implementations,documentation blocks have a respective piece of python code that takesin an RTL output configuration file and breaks it down into the chunksthat ASCII Doc requires and invokes content generation. For example,generating 750 documentation for the integrated circuit may includeinvoking a documentation service with data based on modifiedregister-transfer level data structure and/or the design parameters datastructure.

The process 700 includes generating 760 a field programmable gate arrayemulation data structure (e.g., a field programmable gate arrayemulation file) for the integrated circuit based on the modifiedregister-transfer level data structure and the software development kit.For example, the field programmable gate array emulation data structurefor the integrated circuit may be configured to utilize a cloud basedfield programmable gate array (FPGA). For example, generating 760 afield programmable gate array emulation data structure for theintegrated circuit may include invoking a cloud based FPGA synthesistool. For example, generating 760 a field programmable gate arrayemulation data structure for the integrated circuit may include invokingemulation platforms, such as, Palladium (from Cadence), Veloce (fromMentor Graphics), and/or Zebu (from Synopsys). For example, the fieldprogrammable gate array emulation data structure for the integratedcircuit may be configured to handle emulating devices hard drives andnetwork devices. For example, the field programmable gate arrayemulation data structure may include an emulation file and supportingmaterials. In some implementations, the field programmable gate arrayemulation data structure for the integrated circuit may provide foremulation of a whole system, including peripherals, operating together(e.g., memory timing needs to be matched). For example, the peripheralsemulated may be the actual peripherals a user has selected in the webinterface generated by a web application server. For example, generating760 a field programmable gate array emulation data structure for theintegrated circuit may include highly detailed use of existing toolsbased on the parameterized integrated circuit design. For example,generating 760 a field programmable gate array emulation data structurefor the integrated circuit may include invoking the FPGA/Emulatortoolchain, setting up the emulated devices, and compiling the emulateddevices. For example, generating 760 a field programmable gate arrayemulation data structure for the integrated circuit may include invokinga FPGA/emulation service with data based on modified register-transferlevel data structure and/or the design parameters data structure.

The process 700 includes generating 770 a test plan for an integratedcircuit based on the design parameters data structure and acceptancecriteria. In some implementations, the acceptance criteria are receivedwith the design parameters data structure (e.g., received from a webclient or received from a scripting API client). In someimplementations, the acceptance criteria are read from memory (e.g., thememory 406). For example, generating 770 a test plan for an integratedcircuit may include invoking Verilog simulators (e.g., open sourceVerilog simulators). For example, the test plan for an integratedcircuit may include utilizing FPGAs. For example, the test plan for anintegrated circuit may include utilizing software simulators, such asQuick Emulator (QEMU), Spike, and/or other software simulators. In someimplementations, multiple target test platforms look the same so thetest plan for an integrated circuit may include moving the workloadsacross different cost options (e.g., using physical FPGAs vs. cheaperusing pre-emptible cloud instances). For example, a test plan for anintegrated circuit may be generated 770 based on the modifiedregister-transfer level data structure (e.g., including Verilog RTL),the software development kit, the physical design data structure (e.g.,including a GDSII file), a corpus of tests, and corresponding acceptancecriteria. In some implementations, generating 770 a test plan for anintegrated circuit may include responding to varying acceptance criteriathat are user-defined. Given acceptance criteria and a designconfiguration, a test plan may be generated 770 automatically. Forexample, generating 770 a test plan for an integrated circuit mayinclude defining environments, filtering out tests that cannot be rungiven a corpus of tests and a hardware and software design generatedbased on the design parameters data structure, and generating the testplan to include a sequence of selected tests for the integrated circuitdesign. For example, an environment may define a test platform. Theremay be additional components in a test bench, outside the device undertest, and it may be beneficial to standardize these environments acrossdesigns. For example, a way to end a test may be standardized within atest platform. Some test platforms may define a register a CPU can writeto that is defined within the test bench, while some test platforms willwiggle a general purpose input/output (GPIO) pin in a certain way. Givena test plan, many test platforms may be used for all tests.

The process 700 includes invoking 780 tests for the integrated circuitbased on the test plan, the modified register-transfer level datastructure, the software development kit, and the physical design datastructure to obtain a set of test results. For example, the invoked 780verification tests may be executed directly by a controller, by averification service, and/or by an external service (e.g., a cloud basedFPGA or emulation service that is accessed via communications over anetwork). In some implementations, invoking 780 tests for the integratedcircuit may include invoking a test using a field programmable gatearray, programmed based on the field programmable gate array emulationdata structure, to obtain an emulation result. The field programmablegate array may be operating on a cloud server. For example, invoking 780tests for the integrated circuit may include using credentials (e.g., alogin and/or password) to invoke the test on the field programmable gatearray operating on a cloud server. For example, the test results mayinclude summary information for a large number of tests, such as abinary indication of whether all acceptance criteria were met by thegenerated integrated circuit design, or a list of binary indications ofwhether individual verification tests were passed for respectiveverification tests included in the test plan.

The process 700 includes transmitting, storing, or displaying 790 adesign data structure based on the modified register-transfer level datastructure, the software development kit, the physical design datastructure, and the test results. For example, the design data structuremay be a collection of files, an archive, or a repository (e.g., aGitHub repository) that includes data from the modifiedregister-transfer level data structure, the software development kit,the physical design data structure, and the test results. For example,the design data structure may also include the documentation generated750 and/or the field programmable gate array emulation data structuregenerated 760. For example, the design data structure may be transmitted790 to an external device (e.g., a personal computing device) fordisplay or storage. For example, the design data structure may be stored790 in memory (e.g., the memory 406). For example, design data structuremay be displayed 790 in a user interface (e.g., the user interface 420).For example, the design data structure may be transmitted 790 via anetwork communications interface (e.g., the network communicationsinterface 418).

Although the process 700 is shown as a series of operations for clarity,implementations of the process 700 or any other technique, process, oralgorithm described in connection with the implementations disclosedherein can be performed in various orders or concurrently. Additionally,operations in accordance with this disclosure can be performed withother operations not presented and described herein. Furthermore, one ormore aspects of the systems and techniques described herein can beomitted. For example, operation 750 may be omitted from the process 700.

FIG. 8 is flow chart of an example of a process 800 for fabricating andtesting of an integrated circuit based on a modified register-transferlevel data structure. The process 800 includes generating 810 a physicaldesign data structure for the integrated circuit based on the modifiedregister-transfer level data structure; invoking 820 fabrication of theintegrated circuit based on the physical design data structure; invoking830 tests of the fabricated integrated circuit to obtain a set of testresults; and transmitting, storing, or displaying 840 the set of testresults. For example, the process 800 may be implemented by theintegrated circuit design service infrastructure 310 of FIG. 3. Forexample, the process 800 may be implemented by the system 400 of FIG. 4.For example, the process 800 may be used to quickly incorporate amodular processor design with an input/output shell (e.g., theinput/output shell of the integrated circuit design 100 of FIG. 1),including connecting modules of the design using automatically generatedclock crossings, in a system-on-a-chip design that can be rapidly testedin silicon. This approach may reduce processor development time, reducethe costs of testing a design, and/or improve the quality of testresults.

The process 800 includes generating 810 a physical design data structurefor the integrated circuit based on a modified register-transfer leveldata structure (e.g., a modified register-transfer level data structureobtained using the process 500 of FIG. 5 or the process 600 of FIG. 6).For example, generating 810 a physical design data structure for theintegrated circuit may include invoking a physical design service withdata based on the modified register-transfer level data structure and/orthe design parameters data structure. For example, generating 810 aphysical design data structure for the integrated circuit may includeinvoking synthesis and place & route tools (e.g., Synopsys, Cadence,and/or Mentor tools). For example, generating 810 a physical design datastructure for the integrated circuit may include performing logicalequivalent checking. For example, generating 810 a physical design datastructure for the integrated circuit may include invoking static timinganalysis tools. For example, generating 810 a physical design datastructure for the integrated circuit may include performing design rulechecking (DRC) and/or layout versus schematic (LVS) checking. Forexample, generating 810 a physical design data structure for theintegrated circuit may include determining power, performance, and areaestimates for the resulting integrated circuit design and providingthese estimates as feedback to a user (e.g., a user of a web client).For example, the physical design data structure may include inless-technical terms whether there are any issues with the physicaldesign. For example, the physical design data structure may highlightimportant components of the output of the synthesis and place & routetools. For example, the physical design data structure may include aGDSII file or an OASIS file. For example, generating 810 a physicaldesign data structure for the integrated circuit may include managingand orchestrating physical design toolchains in a cloud. For example,generating 810 a physical design data structure for the integratedcircuit may include handling database movement from tool to tool, andmanaging access to third party IP cores. For example, generating 810 aphysical design data structure for the integrated circuit may includeaccessing template designs, which may allow for significant designreuse. For example, generating 810 a physical design data structure forthe integrated circuit may include identifying those combinations toreduce workload. For example, generating 810 a physical design datastructure for the integrated circuit may provide better or more compacterror/issue reporting, by translating tool issues into manageablefeedback and providing the actual error/output of tools in a deliverableformat to a user (e.g., a user of a web client). For example, generating810 a physical design data structure for the integrated circuit mayinclude using physical design blocks for identified pairings offunctional blocks that may be reused across designs to improveefficiency.

The process 800 includes invoking 820 fabrication of the integratedcircuit based on the physical design data structure. In someimplementations, a physical design specification (e.g., a GDSII file)based on a physical design data structure for the integrated circuit istransmitted via a network (e.g., the network 306) to a manufacturerserver (e.g., the manufacturer server 330) to invoke 820 fabrication ofthe integrated circuit (e.g., using manufacturing equipment of theassociated manufacturer). For example, the manufacturer server 330 mayhost a foundry tape out website that is configured to receive physicaldesign specifications (e.g., as a GDSII file or an OASIS file) toschedule or otherwise facilitate fabrication of integrated circuits. Insome implementations, fabrication of the integrated circuit may beinvoked 820 by direct control of manufacturing equipment (e.g., viacommunication over a bus or serial port).

The process 800 includes invoking 830 tests of the fabricated integratedcircuit to obtain a set of test results. The tests may be performed inthe same facility as the fabrication, or the integrated circuit may bephysically transferred (e.g., via mail) to another facility for testing.The integrated circuit may be connected to testing apparatus, which maybe controlled to invoke 830 tests of the fabricated integrated circuit.For example, invoking 830 tests of the fabricated integrated circuit toobtain a set of test results may include transmitting commands,including parts of a test plan for the integrated circuit, to acloud-based server (e.g., the silicon testing server 340) controllingthe testing apparatus.

The process 800 includes transmitting, storing, or displaying 840 theset of test results. For example, the set of test results may betransmitted 840 to an external device (e.g., a personal computingdevice) for display or storage. For example, the set of test results maybe stored 840 in memory (e.g., the memory 406). For example, set of testresults may be displayed 840 in a user interface (e.g., the userinterface 420). For example, the set of test results may be transmitted840 via a network communications interface (e.g., the networkcommunications interface 418).

FIG. 9 is block diagram of an example of an integrated circuit design900 including the input/output shell of FIG. 1 and custom processorlogic. The integrated circuit 910 includes custom modules (220, 222,230, 232, 234, and 236) in four reset domains: core_1_rst, core_2_rst,tl_rst, and lim_rst; along with interface modules of the input/outputshell (130, 140, 150, and 160) in their four respective reset domains;p_rst, cl_rst, jtag_rst, and usb_rst. A user may quickly merge thecustom processor logic with the input/output shell by issuing commandsto cause reset crossings to be automatically generated between modulesin different reset domains of the integrated circuit 910. In thisexample, the custom processor logic of the integrated circuit design 900includes a first IP core module 220 and a second IP core module 222 thatare connected to a TileLink SBus module 230. The core_1_rst reset domainis a synchronous reset domain with a minimum reset duration of 16 clockcycles. The core_2_rst reset domain is a synchronous reset domain with aminimum reset duration of 24 clock cycles. The tl_rst reset domain is anasynchronous reset domain. The first IP core module 220 is connected tothe TileLink SBus module 230 by a synchronous-to-asynchronous resetcrossing with minimum reset duration of 16 clock cycles (SA16) 940. Thesecond IP core module 222 is connected to the TileLink SBus module 230by a synchronous-to-asynchronous reset crossing with minimum resetduration of 24 clock cycles (SA24) 942. A debug module 232 in the tl_rstreset domain is connected to the JTAG module 150 in the jtag_rst resetdomain by an asynchronous reset crossing (ARC) 952. A mask ROM module234 is also included in the tl_rst reset domain and may be connected tothe TileLink SBus module 230 by intra-reset domain connections (notexplicitly shown in FIG. 9). A LIM SRAM module 236 in the lim_rst resetdomain is connected to the TileLink SBus module 230 by an asynchronousreset crossing (ARC) 944. The ChipLink module 140 in the cl_rst resetdomain is connected to the TileLink SBus module 230 by an asynchronousreset crossing (ARC) 946. The TileLink PBus module 130 in the p_rstreset domain is connected to the TileLink SBus module 230 by anasynchronous reset crossing (ARC) 950. The USB module 160 in the usb_rstreset domain is connected to the TileLink SBus module 230 by anasynchronous reset crossing (ARC) 954. For example, the process 1000 ofFIG. 10 or the process 1100 of FIG. 11 may be implemented to generatethe reset crossings (940, 942, 944, 946, 950, 952, and 954) between themodules of the integrated circuit design 900. The resulting integratedcircuit design 900 may then be rapidly tested using system 300 of FIG.3, the process 700 of FIG. 7 and/or the process 800 of FIG. 8.

FIG. 10 is flow chart of an example of a process 1000 for generating areset crossing of a reset crossing type in an integrated circuit design.The process 1000 includes accessing 1010 a register-transfer level datastructure for an integrated circuit design; receiving 1020 a command togenerate a reset crossing between a first module of theregister-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determining 1030 a signaling protocol identifier for thereset crossing based on data of the second module; responsive to thecommand, automatically determining 1040 a directionality for the resetcrossing based on data of the second module; responsive to the command,automatically generating 1060 the reset crossing between the firstmodule and the second module based on the signaling protocol identifierand based on the directionality to obtain a modified register-transferlevel data structure; and transmitting, storing, or displaying 1070 themodified register-transfer level data structure. For example, theprocess 1000 may be implemented by the system 300 of FIG. 3. Forexample, the process 1000 may be implemented by the system 400 of FIG.4.

The process 1000 includes accessing 1010 a register-transfer level datastructure (e.g., a file, a database, a repository, or a bitstream) foran integrated circuit design. The register-transfer level data structureincludes a logical description of an integrated circuit design. Forexample, the integrated circuit design may be of an IP core. Forexample, the integrated circuit design may be of a processor. Forexample, the integrated circuit design may be of a system-on-a-chip. Insome implementations, the register-transfer level data structure maydescribe a system-on-a-chip including a custom processor and aninput/output shell configured to transfer to and/or from devicesexternal to the system-on-a-chip. For example, the register-transferlevel data structure may describe the integrated circuit of 910 of FIG.9. For example, the register-transfer level data structure may beaccessed 1010 by receiving the register-transfer level data structure(e.g., via network communications using the network communicationsinterface 418). For example, the register-transfer level data structuremay be accessed 1010 by reading the register-transfer level datastructure from memory (e.g., reading from the memory 406 via the bus404).

The process 1000 includes receiving 1020 a command to generate a resetcrossing between a first module of the register-transfer level datastructure and a second module of the register-transfer level datastructure. The command may include a parameter specifying a resetcrossing type (e.g., synchronous with a difference in duration orasynchronous). For example, the command may identify the first moduleand the second module as two modules of the integrated circuit design tobe connected with a reset crossing. For example, the command may includea call to a method of the first module or a method of the second module.In some implementations, the command may have been generated using agraphical user interface that displays graphical representations of themodules of the register-transfer level data structure. For example, thecommand may be part of an application programming interface (API). Forexample, the command may be received 1020 via a user interface (e.g.,the user interface 420). For example, the command may be received 1020via a network interface (e.g., using the network communicationsinterface 418). In some implementations, the command is generated as aresult of a user interface interaction by a human user. In someimplementations, the command is generated by an automatically by an EDAdesign flow.

The process 1000 includes, responsive to the command, automaticallydetermining 1030 a signaling protocol identifier for the reset crossingbased on data of the second module. The signaling protocol identifiermay identify a signaling protocol (e.g., a bus protocol) to be used onthe reset crossing. For example, the signaling protocol used by a resetcrossing may be the AMBA AXI4 protocol, the TileLink protocol, or aninterrupt protocol. For example, the signaling protocol identifier mayinclude text, an integer, or some other data that may be mapped toparticular signaling protocol. In some implementations, the signalingprotocol identifier for the reset crossing is determined 1030 based on abus protocol of the second module (e.g., where the second module is abus). In some implementations, the signaling protocol identifier for thereset crossing is determined 1030 based on data of the first module. Forexample, the signaling protocol identifier for the reset crossing may bedetermined 1030 as corresponding to a signaling protocol that is commonto the first module and the second module. For example, determining 1030the signaling protocol identifier for the reset crossing may includeaccessing a signaling protocol identifier of the first module and/or asignaling protocol identifier of the second module.

The process 1000 includes, responsive to the command, automaticallydetermining 1040 a directionality (e.g., sending vs. receiving or mastervs. slave) for the reset crossing based on data of the second module.For example, the directionality of the reset crossing may be determined1040 as receiving at the first module and sending from the secondmodule. For example, the directionality of the reset crossing may bedetermined 1040 as sending from the first module and receiving at thesecond module. For example, where the second module is a bus, thedirectionality of the reset crossing may be determined 1040 based onwhether the first module is configured to be a master or a slave on thebus.

The process 1000 includes, responsive to the command, automaticallygenerating 1060 the reset crossing between the first module and thesecond module based on the signaling protocol identifier and based onthe directionality to obtain a modified register-transfer level datastructure. For example, the reset crossing may be automaticallygenerated 1060 based on a reset crossing type (e.g., synchronous,synchronous-to-asynchronous, or asynchronous) specified by the command.The reset crossing type may have been chosen based on a reset domaintype of the first module and based on a reset domain type of the secondmodule. For example, a reset crossing type may be parameterized by adifference between the reset durations for the two modules (e.g., asource module and a destination module) that are connected by the resetcrossing. For example, the difference in reset durations may determinehow long a reset signal should be stretched and/or for what periodoutputs passed between the two modules should be suppressed. In someimplementations, the reset domain type of the first module indicates afirst reset duration in clock cycles, the reset domain type of thesecond module indicates a second reset duration in clock cycles, and thereset crossing type indicates a difference between the first resetduration and the second reset duration. For example, when a reset signalfrom an asynchronous reset domain is to be crossed to a synchronousreset domain, a reset crossing of type synchronous-to-asynchronous maybe generated 1060. Generating 1060 a synchronous-to-asynchronous resetcrossing may include generating logic to stretch the reset signal outputdriven to the synchronous reset domain to a length required by thesynchronous reset domain and to suppress outputs from the synchronousdomain during its reset period. For example, a reset crossing type ofasynchronous may be used where two modules being connected are robust toasynchronous reset. For example, an asynchronous reset crossing mayrequire less logic to safely pass signals between the two connectedmodules.

In some implementations, generating 1060 the reset crossing includesusing an implicit class (e.g., an implicit class defined in the SCALAlanguage) that is invoked using the signaling protocol identifier. Insome implementations, generating 1060 the reset crossing includes usingan auto-punching wires method to connect the first module to the secondmodule. For example, the reset crossing may include a logic circuitadded to the first module and a logic circuit added to the second moduleto facilitate passing of signals on one or more conductors across areset domain boundary. In some implementations, automatically generating1060 the reset crossing may include generating register-transfer leveldata implementing logic to stretch a reset signal to meet a minimumreset duration of the first module. For example, some modules withcomplex state (e.g., a processor core) may require multiple clock cycles(e.g., 16, 24, or 32 clock cycles) to complete a reset. To accommodatethis requirement, a shorter duration pulse occurring on an externalreset line or node, which may be asynchronous, may be stretched withlogic including a latch to hold the active value of reset line on a nodeinternal to the module for a duration meeting the minimum reset durationof the module. For example, a stretched reset signal may be synchronizedwith a local clock signal. In some implementations, automaticallygenerating 1060 the reset crossing may include generatingregister-transfer level data implementing logic to suppress one or moreoutputs of the first module in accordance with a bus protocol identifiedby the signaling protocol identifier during a reset period for the firstmodule. For example, some modules may have outputs that can takeindeterminant or errant values during a reset. If such a module willtake longer than a connected module in another reset domain to completeits reset, and the connected module is sensitive to receiving errantvalues, it may be prudent to suppress the outputs from the first modulewhile it completes its reset. For example, logic to suppress outputsduring a reset may directly drive nodes bearing the output signals atdefault, safe voltages during the reset or may utilize an enablefunction or other aspect of a bus protocol to prevent the second modulefrom receiving errant outputs during the reset. The modifiedregister-transfer level data structure (e.g., a file, a database, arepository, or a bitstream) includes the generated 1060 reset crossing.For example, automatically generating 1060 the reset crossing mayinclude implementing the process 1200 of FIG. 12.

For example, the second module may be a bus module. For example, thefirst module may be a processor module and it may be connected by thereset crossing to a bus module (e.g., a TileLink bus) that is in adifferent reset domain of the integrated circuit (e.g., asystem-on-a-chip). In some implementations, the first module is part ofa custom processor design and second module is part of input/outputshell (e.g., the input/output shell of FIG. 1). For example, the firstmodule may include an IP core and the second module may be a componentof an input/output shell for a system-on-a-chip design. In someimplementations, the first module and the second module are both busmodules. For example, the reset crossing may be generated 1060 toinclude logic in the first module and/or the second module to convertsignals from a first bus protocol to a second compatible bus protocoland vice versa.

The process 1000 includes transmitting, storing, or displaying 1070 themodified register-transfer level data structure (e.g., a file, adatabase, a repository, or a bitstream). For example, theregister-transfer level data structure may be transmitted 1070 to anexternal device (e.g., a personal computing device) for display orstorage. For example, the register-transfer level data structure may bestored 1070 in memory (e.g., the memory 406). For example,register-transfer level data structure may be displayed 1070 in a userinterface (e.g., the user interface 420). For example, theregister-transfer level data structure may be transmitted 1070 via anetwork communications interface (e.g., the network communicationsinterface 418).

Although the process 1000 is shown as a series of operations forclarity, implementations of the process 1000 or any other technique,process, or algorithm described in connection with the implementationsdisclosed herein can be performed in various orders or concurrently.Additionally, operations in accordance with this disclosure can beperformed with other operations not presented and described herein. Forexample, the process 1000 of FIG. 10 may repeated to receive 1020additional commands to add additional reset crossings to the modifiedregister-transfer level data structure. Furthermore, one or more aspectsof the systems and techniques described herein can be omitted. Forexample, operation 1030 or the operation 1040 may be omitted from theprocess 1000 where the signaling protocol identifier and/or thedirectionality for the reset crossing are provided as parameters of thecommand received 1020. The process 1000 may enable the generation ofmultiple reset crossings to/from a module that are of different resetcrossing types. For example, the process 1000 may be repeated such thatthe command is a first command and the reset crossing is a first resetcrossing, and the repeated process may include receiving 1010 a secondcommand to generate a second reset crossing between the first module ofthe register-transfer level data structure and a third module of theregister-transfer level data structure; responsive to the secondcommand, automatically determining 1030 a signaling protocol identifierfor the second reset crossing based on data of the third module;responsive to the second command, automatically determining 1040 adirectionality for the second reset crossing based on data of the thirdmodule; and responsive to the second command, automatically generating1060 the second reset crossing between the first module and the thirdmodule based on the signaling protocol identifier for the second resetcrossing and based on the directionality for the second reset crossingto obtain the modified register-transfer level data structure. Thesecond reset crossing may have a different reset crossing type (e.g.,synchronous with a difference in duration, synchronous-to-asynchronous,or asynchronous) than the first reset crossing. For example, a modulemay be connected to two different buses in different reset domains usingdifferent types of reset crossings.

FIG. 11 is flow chart of an example of a process for generating a resetcrossing in an integrated circuit design. In this example, the resetcrossing type (e.g., synchronous with a difference in duration,synchronous-to-asynchronous, or asynchronous) of the reset crossing isautomatically determined based on data of one or more of the modulesbeing connected by the reset crossing. The process 1100 includesaccessing 1110 a register-transfer level data structure for anintegrated circuit design; receiving 1120 a command to generate a resetcrossing between a first module of the register-transfer level datastructure and a second module of the register-transfer level datastructure; responsive to the command, automatically determining 1130 asignaling protocol identifier for the reset crossing based on data ofthe second module; responsive to the command, automatically determining1140 a directionality for the reset crossing based on data of the secondmodule; responsive to the command, automatically determining 1150 areset crossing type for the reset crossing based on a reset domain typeof the first module and based on a reset domain type of the secondmodule; responsive to the command, automatically generating 1160 thereset crossing between the first module and the second module based onthe signaling protocol identifier, based on the directionality, andbased on the reset crossing type to obtain a modified register-transferlevel data structure; and transmitting, storing, or displaying 1170 themodified register-transfer level data structure. For example, theprocess 1100 may be implemented by the system 300 of FIG. 3. Forexample, the process 1100 may be implemented by the system 400 of FIG.4.

The process 1100 includes accessing 1110 a register-transfer level datastructure (e.g., a file, a database, a repository, or a bitstream) foran integrated circuit design. The register-transfer level data structureincludes a logical description of an integrated circuit design. Forexample, the integrated circuit design may be of an IP core. Forexample, the integrated circuit design may be of a processor. Forexample, the integrated circuit design may be of a system-on-a-chip. Insome implementations, the register-transfer level data structure maydescribe a system-on-a-chip including a custom processor and aninput/output shell configured to transfer to and/or from devicesexternal to the system-on-a-chip. For example, the register-transferlevel data structure may describe the integrated circuit of 910 of FIG.9. For example, the register-transfer level data structure may beaccessed 1110 by receiving the register-transfer level data structure(e.g., via network communications using the network communicationsinterface 418). For example, the register-transfer level data structuremay be accessed 1110 by reading the register-transfer level datastructure from memory (e.g., reading from the memory 406 via the bus404).

The process 1100 includes receiving 1120 a command to generate a resetcrossing between a first module of the register-transfer level datastructure and a second module of the register-transfer level datastructure. The command may include a parameter specifying a resetcrossing type (e.g., synchronous with a difference in duration,synchronous-to-asynchronous, or asynchronous). For example, the commandmay identify the first module and the second module as two modules ofthe integrated circuit design to be connected with a reset crossing. Forexample, the command may include a call to a method of the first moduleor a method of the second module. In some implementations, the commandmay have been generated using a graphical user interface that displaysgraphical representations of the modules of the register-transfer leveldata structure. For example, the command may be part of an applicationprogramming interface (API). For example, the command may be received1120 via a user interface (e.g., the user interface 420). For example,the command may be received 1120 via a network interface (e.g., usingthe network communications interface 418). In some implementations, thecommand is generated as a result of a user interface interaction by ahuman user. In some implementations, the command is generated by anautomatically by an EDA design flow.

The process 1100 includes, responsive to the command, automaticallydetermining 1130 a signaling protocol identifier for the reset crossingbased on data of the second module. The signaling protocol identifiermay identify a signaling protocol (e.g., a bus protocol) to be used onthe reset crossing. For example, the signaling protocol used by a resetcrossing may be the AMBA AXI4 protocol, the TileLink protocol, or aninterrupt protocol. For example, the signaling protocol identifier mayinclude text, an integer, or some other data that may be mapped toparticular signaling protocol. In some implementations, the signalingprotocol identifier for the reset crossing is determined 1130 based on abus protocol of the second module (e.g., where the second module is abus). In some implementations, the signaling protocol identifier for thereset crossing is determined 1130 based on data of the first module. Forexample, the signaling protocol identifier for the reset crossing may bedetermined 1130 as corresponding to a signaling protocol that is commonto the first module and the second module. For example, determining 1130the signaling protocol identifier for the reset crossing may includeaccessing a signaling protocol identifier of the first module and/or asignaling protocol identifier of the second module.

The process 1100 includes, responsive to the command, automaticallydetermining 1140 a directionality (e.g., sending vs. receiving or mastervs. slave) for the reset crossing based on data of the second module.For example, the directionality of the reset crossing may be determined1140 as receiving at the first module and sending from the secondmodule. For example, the directionality of the reset crossing may bedetermined 1140 as sending from the first module and receiving at thesecond module. For example, where the second module is a bus, thedirectionality of the reset crossing may be determined 1140 based onwhether the first module is configured to be a master or a slave on thebus.

The process 1100 includes, responsive to the command, automaticallydetermining 1150 a reset crossing type for the reset crossing based on areset domain type of the first module and based on a reset domain typeof the second module. wherein the reset crossing is automaticallygenerated based on the reset crossing type. In some implementations, thereset crossing type is determined as the simplest (e.g., smallest areaor lowest power) applicable reset crossing type given the reset domaintypes of the two modules. For example, a reset crossing type may beparameterized by a difference between the reset durations for the twomodules (e.g., a source module and a destination module) that areconnected by the reset crossing. For example, the difference in resetdurations may determine how long a reset signal should be stretchedand/or for what period outputs passed between the two modules should besuppressed. In some implementations, the reset domain type of the firstmodule indicates a first reset duration in clock cycles, the resetdomain type of the second module indicates a second reset duration inclock cycles, and the reset crossing type indicates a difference betweenthe first reset duration and the second reset duration. For example,when a reset signal from an asynchronous reset domain is to be crossedto a synchronous reset domain, a reset crossing type for the resetcrossing may be automatically determined 1150 to be of typesynchronous-to-asynchronous. For example, a reset crossing type ofasynchronous may be used where two modules being connected are robust toasynchronous reset. For example, an asynchronous reset crossing mayrequire less logic to safely pass signals between the two connectedmodules.

The process 1100 includes, responsive to the command, automaticallygenerating 1160 the reset crossing between the first module and thesecond module based on the signaling protocol identifier and based onthe directionality to obtain a modified register-transfer level datastructure. For example, the reset crossing may be automaticallygenerated 1160 based on the determined 1150 reset crossing type (e.g.,synchronous, synchronous-to-asynchronous, or asynchronous). In someimplementations, generating 1160 the reset crossing includes using animplicit class (e.g., an implicit class defined in the SCALA language)that is invoked using the signaling protocol identifier. In someimplementations, generating 1160 the reset crossing includes using anauto-punching wires method to connect the first module to the secondmodule. For example, the reset crossing may include a logic circuitadded to the first module and a logic circuit added to the second moduleto facilitate passing of signals on one or more conductors across areset domain boundary. In some implementations, automatically generating1160 the reset crossing may include generating register-transfer leveldata implementing logic to stretch a reset signal to meet a minimumreset duration of the first module. For example, some modules withcomplex state (e.g., a processor core) may require multiple clock cycles(e.g., 16, 24, or 32 clock cycles) to complete a reset. To accommodatethis requirement, a shorter duration pulse occurring on an externalreset line or node, which may be asynchronous, may be stretched withlogic including a latch to hold the active value of reset line on a nodeinternal to the module for a duration meeting the minimum reset durationof the module. For example, a stretched reset signal may be synchronizedwith a local clock signal. In some implementations, automaticallygenerating 1160 the reset crossing may include generatingregister-transfer level data implementing logic to suppress one or moreoutputs of the first module in accordance with a bus protocol identifiedby the signaling protocol identifier during a reset period for the firstmodule. For example, some modules may have outputs that can takeindeterminant or errant values during a reset. If such a module willtake longer than a connected module in another reset domain to completeits reset, and the connected module is sensitive to receiving errantvalues, it may be prudent to suppress the outputs from the first modulewhile it completes its reset. For example, logic to suppress outputsduring a reset may directly drive nodes bearing the output signals atdefault, safe voltages during the reset or may utilize an enablefunction or other aspect of a bus protocol to prevent the second modulefrom receiving errant outputs during the reset. The modifiedregister-transfer level data structure (e.g., a file, a database, arepository, or a bitstream) includes the generated 1160 reset crossing.For example, automatically generating 1160 the reset crossing mayinclude implementing the process 1200 of FIG. 12. For example,generating 1160 a synchronous-to-asynchronous reset crossing may includegenerating logic to stretch the reset signal output driven to thesynchronous reset domain to a length required by the synchronous resetdomain and to suppress outputs from the synchronous domain during itsreset period.

For example, the second module may be a bus module. For example, thefirst module may be a processor module and it may be connected by thereset crossing to a bus module (e.g., a TileLink bus) that is in adifferent reset domain of the integrated circuit (e.g., asystem-on-a-chip). In some implementations, the first module is part ofa custom processor design and second module is part of input/outputshell (e.g., the input/output shell of FIG. 1). For example, the firstmodule may include an IP core and the second module may be a componentof an input/output shell for a system-on-a-chip design. In someimplementations, the first module and the second module are both busmodules. For example, the reset crossing may be generated 1160 toinclude logic in the first module and/or the second module to convertsignals from a first bus protocol to a second compatible bus protocoland vice versa.

The process 1100 includes transmitting, storing, or displaying 1170 themodified register-transfer level data structure (e.g., a file, adatabase, a repository, or a bitstream). For example, theregister-transfer level data structure may be transmitted 1170 to anexternal device (e.g., a personal computing device) for display orstorage. For example, the register-transfer level data structure may bestored 1170 in memory (e.g., the memory 406). For example,register-transfer level data structure may be displayed 1170 in a userinterface (e.g., the user interface 420). For example, theregister-transfer level data structure may be transmitted 1170 via anetwork communications interface (e.g., the network communicationsinterface 418).

Although the process 1100 is shown as a series of operations forclarity, implementations of the process 1100 or any other technique,process, or algorithm described in connection with the implementationsdisclosed herein can be performed in various orders or concurrently.Additionally, operations in accordance with this disclosure can beperformed with other operations not presented and described herein. Forexample, the process 1100 of FIG. 11 may repeated to receive 1120additional commands to add additional reset crossings to the modifiedregister-transfer level data structure. Furthermore, one or more aspectsof the systems and techniques described herein can be omitted. Forexample, operation 1130 or the operation 1140 may be omitted from theprocess 1100 where the signaling protocol identifier and/or thedirectionality for the reset crossing are provided as parameters of thecommand received 1120. The process 1100 may enable the generation ofmultiple reset crossings to/from a module that are of different resetcrossing types. For example, the process 1100 may be repeated such thatthe command is a first command and the reset crossing is a first resetcrossing, and the repeated process may include receiving 1110 a secondcommand to generate a second reset crossing between the first module ofthe register-transfer level data structure and a third module of theregister-transfer level data structure; responsive to the secondcommand, automatically determining 1130 a signaling protocol identifierfor the second reset crossing based on data of the third module;responsive to the second command, automatically determining 1140 adirectionality for the second reset crossing based on data of the thirdmodule; and responsive to the second command, automatically generating1160 the second reset crossing between the first module and the thirdmodule based on the signaling protocol identifier for the second resetcrossing and based on the directionality for the second reset crossingto obtain the modified register-transfer level data structure. Thesecond reset crossing may have a different reset crossing type (e.g.,synchronous with a difference in duration, synchronous-to-asynchronous,or asynchronous) than the first reset crossing. For example, a modulemay be connected to two different buses in different reset domains usingdifferent types of reset crossings.

FIG. 12 is flow chart of an example of a process 1200 for generating areset crossing to accommodate a difference in reset durations betweenmodules in different reset domains in an integrated circuit design. Theprocess 1200 includes generating 1210 register-transfer level dataimplementing logic to stretch a reset signal to meet a minimum resetduration of the first module. For example, some modules with complexstate (e.g., a processor core) may require multiple clock cycles (e.g.,16, 24, or 32 clock cycles) to complete a reset. To accommodate thisrequirement, a shorter duration pulse occurring on an external resetline or node, which may be asynchronous, may be stretched with logicincluding a latch to hold the active value of reset line on a nodeinternal to the module for a duration meeting the minimum reset durationof the module. For example, a stretched reset signal may be synchronizedwith a local clock signal.

The process 1200 also includes generating 1220 register-transfer leveldata implementing logic to suppress one or more outputs of the firstmodule in accordance with a bus protocol identified by the signalingprotocol identifier during a reset period for the first module. Forexample, some modules may have outputs that can take indeterminant orerrant values during a reset. If such a module will take longer than aconnected module in another reset domain to complete its reset, and theconnected module is sensitive to receiving errant values, it may beprudent to suppress the outputs from the first module while it completesits reset. For example, logic to suppress outputs during a reset maydirectly drive nodes bearing the output signals at default, safevoltages during the reset or may utilize an enable function or otheraspect of a bus protocol to prevent the second module from receivingerrant outputs during the reset. For example, the logic for suppressingoutputs may include a counter that can be used to maintain a safe statefor predetermined number of clock cycles.

Implementations or portions of implementations of the above disclosurecan take the form of a computer program product accessible from, forexample, a computer-usable or computer-readable medium. Acomputer-usable or computer-readable medium can be any device that can,for example, tangibly contain, store, communicate, or transport aprogram or data structure for use by or in connection with anyprocessor. The medium can be, for example, an electronic, magnetic,optical, electromagnetic, or semiconductor device. Other suitablemediums are also available. Such computer-usable or computer-readablemedia can be referred to as non-transitory memory or media, and caninclude RAM or other volatile memory or storage devices that can changeover time. For example, a non-transitory computer-readable storagemedium may include executable instructions that, when executed by aprocessor, cause performance of an operations to implement the process500 of FIG. 5 or the process 600 of FIG. 6.

Appendix A below is an example of a code snippet in the Scala languagethat can used as part of an implementation of a interface forautomatically generating clock crossings in a an integrated circuitdesign. For example, the code snippet of the Appendix A may be used aspart of an implementation of an interface that can be used to performthe process 500 of FIG. 5 or the process 600 of FIG. 6. Appendix B belowis an example of a code snippet in the Scala language that can used tofacilitate automatically generating a clock crossing between processingcore and system bus in different clock domains. Appendix C below is anexample of a code snippet in the Scala language that can used tofacilitate automatically generating a clock crossing between two busesin different clock domains.

While the disclosure has been described in connection with certainembodiments, it is to be understood that the disclosure is not to belimited to the disclosed embodiments but, on the contrary, is intendedto cover various modifications and equivalent arrangements includedwithin the scope of the appended claims, which scope is to be accordedthe broadest interpretation so as to encompass all such modificationsand equivalent structures.

APPENDIX A  package freechips.rocketchip.tilelink  importfreechips.rocketchip.config.Parameters  importfreechips.rocketchip.diplomacy._(—)  importfreechips.rocketchip.util.RationalDirection  case classTLInwardCrossingHelper(name: String, scope: LazyScope, node: TLInwardNode) {   def apply(xing: ClockCrossingType =NoCrossing)(implicit p: Parameters):  TLInwardNode = {    xing match {    case AsynchronousCrossing(depth, sync) =>      node :*=* scope {TLAsyncCrossingSink(depth, sync) :*=*  TLAsyncNameNode(name) } :*=*TLAsyncCrossingSource(sync)     case RationalCrossing(direction) =>     node :*=* scope { TLRationalCrossingSink(direction.flip) :*=* TLRationalNameNode(name) } :*=* TLRationalCrossingSource( )     caseSynchronousCrossing(buffer) =>      node :*=* scope { TLBuffer(buffer):*=* TLNameNode(name) }    }   }  }  case classTLOutwardCrossingHelper(name: String, scope: LazyScope, node: TLOutwardNode) {   def apply(xing: ClockCrossingType =NoCrossing)(implicit p: Parameters):  TLOutwardNode = {    xing match {    case AsynchronousCrossing(depth, sync) =>     TLAsyncCrossingSink(depth, sync) :*=* scope {     TLAsyncNameNode(name) :*=*  TLAsyncCrossingSource(sync) } :*=* node    case RationalCrossing(direction) =>     TLRationalCrossingSink(direction) :*=* scope {     TLRationalNameNode(name) :*=*  TLRationalCrossingSource( ) } :*=*node     case SynchronousCrossing(buffer) =>      scope {TLNameNode(name) :*=* TLBuffer(buffer) } :*=* node    }   } }

APPENDIX B protected def connectMasterPortsToSBus(tile: BaseTile,crossing: RocketCrossingParams) {  sbus.fromTile(tile.tileParams.name,crossing.master.buffers) {   crossing.master.cork    .map { u =>TLCacheCork(unsafe = u) }    .map { _ :=* tile.crossMasterPort( ) }   .getOrElse { tile.crossMasterPort( ) }  } }

APPENDIX C  /** Example Top with periphery devices and ports, and aRocket subsystem */  class ExampleRocketSystem(implicit p: Parameters)extends RocketSubsystem    with HasAsyncExtInterrupts    withCanHaveMasterAXI4MemPort    with CanHaveMasterAXI4MMIOPort    withCanHaveSlaveAXI4Port    with HasPeripheryBootROM {   override lazy valmodule = new ExampleRocketSystemModuleImp(this)   // The sbus mastersthe cbus; here we convert TL-UH −> TL-UL   sbus.crossToBus(cbus,NoCrossing)   // The cbus masters the pbus; which might be clockedslower   cbus.crossToBus(pbus, SynchronousCrossing( ))   // The fbusmasters the sbus; both are TL-UH or TL-C   FlipRendering { implicit p =>   sbus.crossFromBus(fbus, SynchronousCrossing( ))   }   // The sbusmasters the mbus; here we convert TL-C −> TL-UH   private valBankedL2Params(nBanks, coherenceManager) = p(BankedL2Key)   private val(in, out, halt) = coherenceManager(this)   if (nBanks != 0) {   sbus.coupleTo(“coherence_manager”) { in :*= _ }   mbus.coupleFrom(“coherence_manager”) { _ :=*BankBinder(mbus.blockBytes *  (nBanks−1)) :*= out}   } }

What is claimed is:
 1. A non-transitory computer-readable storage mediumthat includes instructions that, when executed by a processor,facilitate performance of operations comprising: accessing aregister-transfer level data structure for an integrated circuit design;receiving a command to generate a reset crossing between a first moduleof the register-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determining a signaling protocol identifier for the resetcrossing based on data of the second module; responsive to the command,automatically determining a directionality for the reset crossing basedon data of the second module; and responsive to the command,automatically generating the reset crossing between the first module andthe second module based on the signaling protocol identifier and basedon the directionality to obtain a modified register-transfer level datastructure.
 2. The non-transitory computer-readable storage medium ofclaim 1, wherein the instructions include instructions that, whenexecuted by a processor, facilitate performance of operationscomprising: responsive to the command, automatically determining a resetcrossing type for the reset crossing based on a reset domain type of thefirst module and based on a reset domain type of the second module,wherein the reset crossing is automatically generated based on the resetcrossing type.
 3. The non-transitory computer-readable storage medium ofclaim 2, wherein the reset domain type of the first module indicates afirst reset duration in clock cycles, the reset domain type of thesecond module indicates a second reset duration in clock cycles, and thereset crossing type indicates a difference between the first resetduration and the second reset duration.
 4. The non-transitorycomputer-readable storage medium of claim 1, wherein the commandincludes a parameter specifying a reset crossing type and the resetcrossing is automatically generated based on the reset crossing typespecified by the command.
 5. The non-transitory computer-readablestorage medium of claim 1, wherein automatically generating the resetcrossing comprises: generating register-transfer level data implementinglogic to suppress one or more outputs of the first module in accordancewith a bus protocol identified by the signaling protocol identifierduring a reset period for the first module.
 6. The non-transitorycomputer-readable storage medium of claim 1, wherein automaticallygenerating the reset crossing comprises: generating register-transferlevel data implementing logic to stretch a reset signal to meet aminimum reset duration of the first module.
 7. The non-transitorycomputer-readable storage medium of claim 1, wherein automaticallygenerating the reset crossing comprises: using an implicit class that isinvoked using the signaling protocol identifier.
 8. The non-transitorycomputer-readable storage medium of claim 1, wherein the second moduleis a bus module.
 9. The non-transitory computer-readable storage mediumof claim 1, wherein the first module includes an IP core and the secondmodule is a component of an input/output shell for a system-on-a-chipdesign.
 10. The non-transitory computer-readable storage medium of claim1, wherein the instructions include instructions that, when executed bya processor, facilitate performance of operations comprising: generatinga physical design data structure for the integrated circuit based on themodified register-transfer level data structure; invoking fabrication ofthe integrated circuit based on the physical design data structure;invoking tests of the fabricated integrated circuit to obtain a set oftest results; and transmitting, storing, or displaying the set of testresults.
 11. The non-transitory computer-readable storage medium ofclaim 1, wherein the instructions include instructions that, whenexecuted by a processor, facilitate performance of operationscomprising: generating a physical design data structure for theintegrated circuit based on the modified register-transfer level datastructure; generating a software development kit for the integratedcircuit based on the modified register-transfer level data structure;generating a test plan for the integrated circuit; invoking tests forthe integrated circuit based on the test plan, the modifiedregister-transfer level data structure, the software development kit,and the physical design data structure to obtain a set of test results;and transmitting, storing, or displaying a design data structure basedon the modified register-transfer level data structure, the softwaredevelopment kit, the physical design data structure, and the testresults.
 12. A system comprising: a network interface; a memory; and aprocessor, wherein the memory includes instructions executable by theprocessor to cause the system to: access a register-transfer level datastructure for an integrated circuit design; receive a command togenerate a reset crossing between a first module of theregister-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determine a signaling protocol identifier for the resetcrossing based on data of the second module; responsive to the command,automatically determine a directionality for the reset crossing based ondata of the second module; and responsive to the command, automaticallygenerate the reset crossing between the first module and the secondmodule based on the signaling protocol identifier and based on thedirectionality to obtain a modified register-transfer level datastructure.
 13. The system of claim 12, wherein the memory furtherincludes instructions executable by the processor to cause the systemto: responsive to the command, automatically determine a reset crossingtype for the reset crossing based on a reset domain type of the firstmodule and based on a reset domain type of the second module, whereinthe reset crossing is automatically generated based on the resetcrossing type.
 14. The system of claim 13, wherein the reset domain typeof the first module indicates a first reset duration in clock cycles,the reset domain type of the second module indicates a second resetduration in clock cycles, and the reset crossing type indicates adifference between the first reset duration and the second resetduration.
 15. The system of claim 12, wherein the command includes aparameter specifying a reset crossing type and the reset crossing isautomatically generated based on the reset crossing type specified bythe command.
 16. The system of claim 12, wherein automaticallygenerating the reset crossing comprises: generating register-transferlevel data implementing logic to suppress one or more outputs of thefirst module in accordance with a bus protocol identified by thesignaling protocol identifier during a reset period for the firstmodule.
 17. The system of claim 12, wherein automatically generating thereset crossing comprises: generating register-transfer level dataimplementing logic to stretch a reset signal to meet a minimum resetduration of the first module.
 18. The system of claim 12, whereinautomatically generating the reset crossing comprises: using an implicitclass that is invoked using the signaling protocol identifier.
 19. Thesystem of claim 12, wherein the first module includes an IP core and thesecond module is a component of an input/output shell for asystem-on-a-chip design.
 20. A method comprising: accessing aregister-transfer level data structure for an integrated circuit design;receiving a command to generate a reset crossing between a first moduleof the register-transfer level data structure and a second module of theregister-transfer level data structure; responsive to the command,automatically determining a signaling protocol identifier for the resetcrossing based on data of the second module; and responsive to thecommand, automatically generating the reset crossing between the firstmodule and the second module based on the signaling protocol identifierto obtain a modified register-transfer level data structure.